Deicer composition



United States Patent 3,227,654 DETCER CONIPUSITIGN Norman W. Standish, Shaker Heights, and Ernest C. Milherger, Maple Heights, Ghio, assignors to The Standard ()il Company, Cleveland, ()hio, a corporation of Ohio No Drawing. Filed Nov. 7,1962, Ser. No. 236,140 7 Claims. (Cl. 252-70) This invention relates to a chemical deicer process and more particularly pertains to a method for melting ice and removing ice from surfaces by treatment with a mixture of urea and an alkali metal nitrite.

The use of freezing point depressants, such as sodium chloride and calcium chloride, as chemical deicers is well known. Both of these compounds are relatively inexpensive, they are quite effective in melting ice and snow at sub-freezing temperatures, and they are used extensively as dei'cers.

In recent years, because of the tremendous increase in motor vehicle trailic, these ice-melting chloride salts have found widespread used in the melting of ice and snow on driveways, streets, roads, bridges and other vehicular roadways. Such materials are soluble in water so that no disposal problem exists as in the case of cinders, slag, sand, or other purely abrasive materials. These latter materials are water-insoluble, and during melting and thawing periods, are washed off the roadways and clog catch basins, sewer lines, etc. The ice-melting salts, on the contrary, create no such problem and although their initial cost per pound is higher than cinders or related abrasive type materials, the over-all costs of these deicing salts frequently are lower as there are fewer maintenance problems encountered.

It is Well known that chlorides of sodium and calcium are extremely corrosive to steel, particularly in the dilute solutions encountered on roadways where these deicing salts are diluted by melting snow, ice or rain. Several inhibitors have been developed for use with the chlorides such as the alkali metal chromates and the like. These inhibiting salts have reduced somewhat the corrosion of the underbodies of trucks, passenger cars, etc.; although the localized pitting type of corrosion which chlorides produce upon aluminum and its alloys still takes place and is a very serious problem which must be solved.

Although the protection against the corrosion of stee by the alkali metal chlorides can be minimized by the use of additives, certain other metals which are used in vehicle construction, such as aluminum and its alloys, are still highly susceptible to chloride corrosion. Aluminum alloys and alloys of ferrous metals are components of aircraft, railroad cars, buses, trucks and other vehicles; and it is one object of this invention to minimize corrosion of these metals which are subject to contact with the deicing salt solution resulting from the melted ice and snow.

Aluminum and its alloys, and particularly highly stressed aluminum and its alloys such as auto parts constructed by stamping techniques, are attacked in such a local manner by the chloride ion that chloride salts cannot be used safely where they will be splashed upon the stressed aluminum or aluminum alloy surface. The inhibiting salts, such as chromates, seem to have no effect on reducing the pitting-type of corrosion which the chlorides cause on aluminum or its alloys.

It is quite well known to those skilled in the art that the term eutectic denotes a minimum in the freezing point versus composition curve of a system and that the particular mixture which exists as liquid or solid at this minimum temperature is the eutectic mixture. It is also well known by those skilled in the art that the temperature at which a solid changes to a liquid is called 3,227,654 Patented Jan. 4, 1966 ice its melting point and that the freezing point is the temperature at which a liquid changes to a solid so'that both points are the same for a given substance. It is apparent, then, that the freezing points or temperatures mentioned herein also mean the melting points or temperatures of the particular system described and, of course, the converse is also true.

A number of salts and salt mixtures have been used as refrigerants or hold-overs. As a refrigerant composition, the mixture must remain liquid at all temperatures of the particular application so that it can be circulated throughout the cooling system. A hold-over composition is frozen during the operation of the refrigerating apparatus forming a cryohydrate which, in turn, melts during the idle refrigeration period and withdraws its latent heat of fusion from the chamber to be cooled, thus maintaining the desired temperature. In the case of a refrigerant, the lowest possible freezing point is desirable. This will result from using the highest concentration of salt or salts which can be obtained in the solutions. In the case of a hold-over composition, a very high negative heat of fusion is also desirable. With both the refrigerant and the hold-over, the composition of the useful mixture is always constant.

On the other hand, a chemical deicer functions in a manner which is completely different from that of a refrigerant or hold-over. In the deicing process, there is initially a limited supply of liquid water available on the surface of the ice and a large excess of deicer. As melting proceeds and water forms, the composition of the solution changes, the temperature of the composition varies, the area of the deicer exposed changes, and the solution temperature either increases or decreases depending on a negative or positive heat of solution of the deicer. Thus, at no time are the composition or physical characteristics of the mixture constant. A measure of the temperature of a mixture of deicer and ice is a measure of the composite effect of all these changing factors which generally gives a higher temperature than the freezing point. For a given salt the deicing tem perature and the freezing temperature eutectic are different and the type and degree of difference is not predictable. Sodium chloride, for instance, has a freezing temperature eutectic of -22.4 F. and it has a deicing temperature of -6 F.

It is an object of the present invention to provide a chemical deicer which, even at sub-freezing temperatures, rapidly wets and melts ice when applied thereto. It is another object to provide a chemical deicer which is not injurious to soil or plant life but to the contrary is actually composed solely of plant nutrients. It is another object to provide a chemical deicer which will not cause corrosion or discoloration of surfaces, and particularly steel, stressed aluminum and aluminum alloy surfaces with which it may come in contact. That these and other objects have been accomplished by the present invention will become apparent from the following description and illustrative examples.

The chemical deicer of this invention has a deicing temperature no greater than 5 F. and comprises an intimate mixture of from 5 to by Weight of urea and from to 15% by weight of an alkali metal nitrite. More highly preferred in the present invention is the chemical deicer possessing a deicing temperature of less than about l0 F. comprising from 18 to 80% by weight of urea and from 82 to 20% by Weight of an alkali metal nitrite.

The chemical deicer of the present invention is a chloride-free deicer which has a marked depressing action on the melting point of ice and which is essentially harmless to most surfaces with which it may come in contact,

including ferrous metals, aluminum and its alloys, asphalt and concrete. Moreover, the deicer embodied in this invention is comparable as an ice melter on a weight basis with the alkali metal chlorides.

The present discovery is particularly useful in conjunction with the melting of ice and snow in driveways and walkways. The chemical deicer embodied in this invention is useful also in the melting of ice and snow on airport runways, bus and truck loading areas, etc. where much of the equipment used is constructed of metals including steel and aluminum.

The chemical deicer embodied herein may be prepared in any convenient fashion providing an intimate mixture of the two essential components results. In a preferred procedure the individual components may be dry-mixed in a pebble or ball-mill, for instance, until an intimately mixed powder results. The desired proportions of urea and alkali metal nitrite can be mixed and heated until molten and the melt can then be cooled and granulated or pulverized. Care must be observed to maintain the temperature of the melt below about 150 C. and preferably below about 110 C. in order to avoid the reaction between urea and the alkali metal nitrite which forms the alkali metal cyanate as disclosed in US. Patent No. 2,665,968. Similarly, in another highly preferred manner, an aqueous solution of the desired proportions of urea and alkali metal nitrite may be prepared followed by removal of the water by evaporation and granulation or grinding of the solid. For instance, a fairly concentrated aqueous solution of the desired proportions of urea and sodium nitrite may be added to a continuous drum drier to produce flakes, or the aqueous solution, or the molten mixture, may be subjected to treatment in a prilling tower which results in a prilled product of granular form. In any event, the method whereby the deicing composition embodied herein is prepared is not critical and is without the scope of the present invention. Any method which produces an intimate mixture of solid urea and alkali metal nitrite in particulate form may be used.

The deicer composition of the present invention is applied to an ice-covered surface, such as a roadway, by broadcasting. The deicer is not blown from the ice surface by the wind because rapid melting follows at points where the deicer contacts the ice and the liquid area spreads rapidly as the melting process continues.

In the following illustrative examples the amounts of the various ingredients are expressed as parts by weight unless otherwise indicated.

Example 1 A blend of 50 parts of urea and 50 parts of sodium nitrite was fused with heat (91 to 100 C.) and the melt was thoroughly mixed. The mixture was then allowed to cool to room temperature and the solid cake was granulated to form a coarse, granular material. To 200 g. of crushed ice were added 100 g. of the aforementioned granular material and the resulting ice-salt mixture was stirred and the deicing temperature attained was found to be F. The deicing temperature is the lowest temperature observed while the above mixture of ice, water and urea-sodium nitrite was being stirred. A deicing temperature of -15 F. was again observed when the foregoing procedure was repeated.

When the foregoing procedure was repeated starting with a :50 by weight mixture of urea and potassium nitrite, a deicing temperature of 16 F. was observed.

When the foregoing procedure was repeated starting with urea alone in place of the urea-sodium nitrite mixture, a deicing temperature of +11 F. was observed.

When the foregoing procedure was repeated using sodium nitrite alone in place of the urea-sodium nitrite mixture, a deicing temperature of 3 F. was observed.

4 Example II The procedure of Example I was repeated, starting with a 5:95 by weight mixture of urea:sodium nitrite. A deicing tcmperature of 5 F was observed.

Example III The'procedure of Example I was repeated, starting with an 85:15 by weight mixture of urea:sodium nitrite. A deicing temperature of 5 F. was observed.

Example IV The procedure of Example I was repeated, starting with and 18:82 by weight mixture of urea:sodium nitrite. A deicing temperature of 10" F. was observed.

Example V Example VI The procedure of Example I was repeated, starting with a 30:70 by weight mixture of urea-sodium nitrite. A deicing temperature of 14 F. was observed.

When the foregoing was repeated using potassium nitrite in place of the sodium nitrite, a deicing temperature of 18 F. was observed.

Example VII The procedure of Example I was repeated, starting with a :30 by weight mixture of urea:sodium nitrite. A deicing temperature of -14 F. was observed.

The surface of metal panels completely coated with acrylic paint, lacquer and enamel was coated with a 10% by weight aqueous solution of the above deicer and the water was allowed to evaporate at room temperature. The panel surface was then wiped and buffed. No apparent change in the surface appearance, gloss, etc. was observed. When the 10% aqueous solution of the above deicer was applied to nylon and to wool carpeting and allowed to dry, a fluffy residue was left which disappeared upon slight brushing of the carpet. The above deicer was superior to calcium chloride and to sodium chloride in this respect.

We claim:

1. The process for melting ice comprising adding to ice a particulate solid deicer having a deicing temperature no higher than about 10 F., consisting of an intimate mixture of from 18 to by weight of urea and from 82 to 20% by weight of an alkali metal nitrite selected from the group consisting of sodium nitrite and potassium nitrite.

2. The process of claim 1 wherein the alkali metal nitrite is sodium nitrite.

3. The process of claim 1 wherein the alkali metal nitrite is potassium nitrite.

4. The process for melting ice comprising adding to ice a particulate solid deicer having a deicing temperature no higher than about 15 F., consisting of an intimate mixture of 50% by weight of urea and 50% by weight of sodium nitrite.

5. The process for melting ice comprising adding to ice a particulate solid deicer having a deicing temperature:

no higher than about-10 F., consisting of an intimate:

mixture of 80% by weight of urea and 20% by weight; of sodium nitrite.

6. A process for melting ice comprising adding to icea particulate solid deicer having a deicing temperature no consisting Of an intimate higher than about *20 F.,

5 6 mixture of 80% by weight of urea and 20% by weight References Cited by the Examiner of potassium nitrite.

7. The process for melting ice comprising adding to ice UNITED STATES PATENTS a particulate solid deicer having a deicing temperature no 2,716,068 8 /1955 Fain et a1, 252-70 XR higher than about -l4 F., cosisting of an intimate miX- 5 2,980,620 4/1961 Hatch 25270 ture of 70% by weight of urea and 30% by weight of sodium nitrite. JULIUS GREENWALD, Primary Examiner. 

1. THE PROCESS FOR MELTING ICE COMPRISING ADDING TO ICE A PARTICULATE SOLID DEICER HAVING A DEICING TEMPERTURE NO HIGHER THAN ABOUT -10*F., CONSISTING OF AN INTIMATE MIXTURE OF FROM 18 TO 80% BY WEIGHT OF UREA AND FROM 82 TO 20% BY WEIGHT OF AN ALKALI METAL NITRITE SELECTED FROM THE GROUP CONSISTING OF SODIUM NITRITE AND POTASSIUM NITRITE. 